The present invention relates to an image forming apparatus in which, for example, a unit such as a secondary transfer unit is installed on an image forming apparatus main body side of an opening/closing cover.
Recently, electrophotographic image forming apparatuses that are capable of forming a multi-color image, such as color copy machines, color printers, and so forth, have been developed.
As electrophotographic image forming apparatuses, for example, intermediate transfer-type color image forming apparatuses are known in which image forming is performed by forming toner images of each color on image carriers such as photosensitive drums, sequentially layering and transferring the toner images of each color to an intermediate transfer belt serving as an intermediate transfer body to form a multi-color image, and then transferring that multi-color image to a recording paper serving as a transfer paper in a nip portion between the intermediate transfer belt and a transfer belt of a secondary transfer unit, and fixing the multi-color image.
In this intermediate transfer-type color image forming apparatus, the secondary transfer unit is provided on an image forming apparatus main body side of a cover capable of opening/closing relative to an opening portion of the image forming apparatus main body, so when a paper jam occurs in the nip portion, the jammed paper can be removed by opening the cover.
In JP 2004-20574A (referred to below as Patent Document 1), a configuration is disclosed in which a secondary transfer roller is provided in an opening/closing cover, and such that a shaft of the transfer roller can be received and thus positioned by a guide provided in the intermediate transfer belt when the opening/closing cover has been closed, the transfer roller shaft is guided along a path in a straight line joining the shaft of the transfer roller and a shaft of a drive roller of the intermediate transfer belt.
Incidentally, in an image forming apparatus in which the secondary transfer unit has been mounted on the image forming apparatus main body side of the opening/closing cover having a fulcrum, in consideration of contact between the rotational track of the secondary transfer unit and other components of the image forming apparatus main body side, it is necessary for the rotational fulcrum to be set at a position as far as possible to the image forming apparatus main body side from the secondary transfer unit, or to enlarge the rotational radius, or the like. Therefore, in design it is necessary to secure sufficient distance between the secondary transfer unit and components on the image forming apparatus main body side.
On the other hand, also when the opening/closing cover has been opened/closed parallel to the image forming apparatus main body via a slide rail or the like rather than a rotational fulcrum, there is the problem of, for example, contact between components on the image forming apparatus main body side and the secondary transfer belt.
In Patent Document 1, when providing a transfer-related member on the back side of the opening/closing cover, it is conceivable that the size in the height direction is restricted in the rotational track of the transfer-related member when opening/closing the opening/closing cover.
Also, in an image forming apparatus in which the secondary transfer unit has been mounted on the image forming apparatus main body side of the opening/closing cover, a transfer pressing contact load is applied as-is to the secondary transfer unit, and because that load is applied to the opening/closing cover, there is a risk of deformation of the opening/closing cover when closing the opening/closing cover.
As a specific example, as shown in FIG. 11, assuming that a pressing force (transfer pressing contact load) of 6 kg is applied to a secondary transfer unit 1000, a load of 3 kg is applied on both the upper side and the lower side of the opening/closing cover where the secondary transfer unit 1000 has been mounted (installed) on the image forming apparatus main body side.
In order to achieve increased strength of the opening/closing cover, for example, it is necessary to prevent deformation with a separate member such as a metal frame or the like. However, this leads to increased cost and weight and so forth, and in the worst case it is conceivable that it will not be possible to secure secondary transfer pressure.
In Patent Document 1, because the load of the transfer roller is applied as-is to the opening/closing cover, the opening/closing cover bulges, and in order to prevent that bulging it is necessary to increase the strength of the opening/closing cover itself.